Mail item

ABSTRACT

A mail item incorporating an information block which provides a three-dimensional array of addressable data elements for storing information, wherein the thee-dimensional array defines a plurality of layers to which information can be written.

The present invention relates to a mail item, in particular a re-usablemail item.

Mail items are printed with information, increasingly with bar codes, asone-dimensional or two-dimensional information blocks.

It is an aim of the present invention to provide a mail item whichincorporates an information block which provides a three-dimensionalarray of addressable data elements for storing information, and inparticular a mail item which is re-usable, such that, on each use,information is written to a different layer of the information block.The present applicant has recognized that optical memory, such asdisclosed in U.S. Pat. No. 5,268,862 and U.S. Pat. No. 5,472,759, thecontents of which are herein incorporated by reference, could be adaptedfor use in a mail item.

In one aspect the present invention provides a mail item incorporatingan information block which provides a three-dimensional array ofaddressable data elements for storing information, wherein thethree-dimensional array defines a plurality of layers to whichinformation can be written.

Preferably, the information block comprises a carrier including aphotochromic storage material having first and second states, and areadout material for providing an indication of the state of the storagematerial at its location.

Preferably, the stored information includes encoded information.

In one embodiment the encoded information is encrypted information.

In another embodiment the encoded information iscryptographically-signed information.

In one embodiment the information block comprises an applied coating.

In another embodiment the information block defines at least part of abody of the mail item.

In one embodiment the mail item comprises a container.

In another embodiment the mail item comprises an envelope.

Preferably, the mail item is re-usable, such that, on each use,information is written to a different layer of the information block.

In another aspect the present invention relates to use, as a re-usableitem, of a mail item incorporating an information block which provides athree-dimensional array of addressable data elements for storinginformation, with the three-dimensional array defining a plurality oflayers to which information can be written.

In a further aspect the present invention provides a mail handlingsystem, comprising: an information reader for reading information froman information block, as a three-dimensional array of addressable dataelements, incorporated in a mail item, with the three-dimensional arraydefining a plurality of layers to which information can be written, andidentifying the last written layer in which information is stored; andan information writer for writing new information in a subsequent layerof the three-dimensional array of the information block.

Preferably, the information writer is configured such as to over-writethe last written layer of the three-dimensional array of the informationblock and thereby zeroise that layer.

Preferred embodiments of the present invention will now be describedhereinbelow by way of example only with reference to the accompanyingdrawings, in which:

FIG. 1 illustrates a fragmentary view of a mail item in accordance witha preferred embodiment of the present invention;

FIG. 2 schematically illustrates a data writer for writing to the mailitem of FIG. 1 in accordance with a first embodiment of the presentinvention;

FIG. 3 schematically illustrates a data writer for writing to the mailitem of FIG. 1 in accordance with a second embodiment of the presentinvention;

FIG. 4 schematically illustrates a data reader for reading from the mailitem of FIG. 1 in accordance with a preferred embodiment of the presentinvention; and

FIG. 5 illustrates a mail handling system in accordance with a preferredembodiment of the present invention.

FIG. 1 illustrates a mail item 1 in accordance with a preferredembodiment of the present invention.

The mail item 1 comprises a body 3 and an information block 5, in thisembodiment applied as a coating to the body 3, which provides athree-dimensional array of optically-addressable data elements 7 whichare each individually writeable using a writing beam and readable usinga reading beam. In an alternative embodiment the information block 5could be formed as part of the body 3. As will be described in moredetail hereinbelow, the data elements 7 are each addressable bydirecting a light beam at any addressable location within theinformation block 5.

In this embodiment the information block 5 is a continuous structure andthe resolution of the data elements 7 is principally determined by theintensity of the writing beam and the optical spatial resolution, withthe resolution being such as to avoid cross-talk between adjacent dataelements 7 in writing and reading operations. The information block 5can be conceptualized as a plurality of stacked pages, each comprising atwo-dimensional array of addressable data elements 7.

In this embodiment the information block 5 comprises a carrier whichincludes throughout a photochromic storage material which has first andsecond states, and a readout material which provides an indication ofthe state of the storage material at its location. In this embodimentthe storage material is a material which changes state from a firststate to a second state in response to two-photon absorption, that is,the simultaneous absorption of two visible-light photons correspondingto ultraviolet (UV) light. In this embodiment the readout material is amaterial which is responsive to one-photon absorption.

In this embodiment the carrier is a polymeric material. In preferredembodiments the polymeric material comprises polyvinylbutyral,polymethylmethacrylate, doped polymethylmethacrylate, such aspolymethylmethacrylate doped with 2-methyl-4-nitroaniline orpolymethylmethacrylate doped with para-nitroaniline, polyvinylacetate,potassium dihydrogen phosphate, UV-curable urethane acrylate polymer orUV-curable epoxy polymer.

In this embodiment the storage material is a fulgide, whichadvantageously provides for thermal stability and relatively long dataretention. In preferred embodiments the storage material comprisesE-Adamantylidene [1-(2,5-dimethyl-3-furyl) ethylidene] succinicanhydride, 1-(2,5-dimethyl-3-furyl) ethylidene (isopropylidene) succinicanhydride, 2,3-bis(2,4,5-trimethyl-3-thienyl) maleic anhydride,cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl) ethene,1,2-dicyano-1,2-bis(2-methylbenzothiophene-3-yl) ethene, or2,3-bis(1,2-dimethyl-3-indolyl) maleic anhydride, and mixtures thereof.

In this embodiment the readout material comprises a fluorescent signaldye which fluoresces when illuminated only when the storage material isin a first state, and does not fluoresce, or fluoresces weakly, whenilluminated when the storage material is in a second state. In preferredembodiments the signal material comprises 3,3′-diethyloxadicarbocyanineiodide, Nile Red dye, Pyridine-1, Pyridine-2,4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino styryl)-4 H-pyran,2[4-(4-dimethylaminophenyl)-1,3-butadienyl]-3-ethylbenzothiazoliump-toluenesulfonate, or1,1′,3,3,3′,3′-hexamethyl-4,4′,5,5′-dibenzo-2,2′,indotricarbocyanineperchlorate, and mixtures thereof.

In another embodiment the carrier can include throughout a frequencyup-conversion material which enables data writing to be performed bylight which has a wavelength which is other than the two-photonabsorption wavelength of the storage material. The up-conversionmaterial has efficient two-photon absorption at the operating wavelengthof the light of the writing beam, and re-emits light at a wavelengthregion which is very efficient for converting the storage material fromthe first to the second state, such as from a colour state to a bleachstate. For example, the writing beam can comprise infra-red light whichis converted to visible light by the frequency up-conversion material.Preferred up-conversion materials are those based on second-harmonicgeneration or two-photon absorption-induced fluorescence. In preferredembodiments the up-conversion material comprises a frequencyup-conversion dye, such as Coumarin 6, 8-hydroxyl-1,36-pyrenetrisulfonic acid or polymethylmethacrylate doped with a materialhaving a high second order non-linear hyperpolarizability, such as2-methyl-4-nitroaniline.

FIG. 2 illustrates a data writer 11 for writing to the information block5 of the mail item 1 in accordance with a first embodiment of thepresent invention.

The data writer 11 comprises a light source 13 for providing acollimated light beam 15, and a lens 17 for focussing the collimatedlight beam 15 to provide a converging writing beam 19 which can befocussed at any location within the information block 5 of the mail item1, and thereby provide for writing to any of the data elements 7 definedby the information block 5. In this embodiment the energy density of thewriting beam 19 is insufficient to result in two-photon absorption atany location in the information block 5 other than at the location ofthe focal point of the writing beam 19. Thus, any of the data elements 7can be individually addressed without effecting adjacent data elements7, that is, without any cross-talk with adjacent data elements 7.

FIG. 3 illustrates a data writer 21 for writing to the information block5 of the mail item 1 in accordance with a second embodiment of thepresent invention.

The data writer 21 comprises first and second light sources 23 a, b forproviding first and second collimated light beams 25 a, b, and first andsecond lenses 27 a, b for focussing the respective ones of thecollimated light beams 25 a, b to provide first and second convergingwriting beams 29 a, b which can be focussed at any common locationwithin the information block 5 of the mail item 1, and thereby providefor writing to any of the data elements 7 defined by the informationblock 5. In this embodiment the energy density of each of the writingbeams 29 a, b is alone insufficient to result in two-photon absorptionat any location in the information block 5, but the first and secondwriting beams 29 a, b together have sufficient energy density at thefocussed common location to provide two-photon absorption. Thus, any ofthe data elements 7 can be individually addressed without effectingadjacent data elements 7, that is, without any cross-talk with adjacentdata elements 7.

FIG. 4 illustrates a data reader 31 for reading from the informationblock 5 of the mail item 1 in accordance with a preferred embodiment ofthe present invention.

The data reader 31 comprises an illumination unit 33 for illuminatingany location which corresponds to a data element 7 within theinformation block 5 of the mail item 1, and a detector 35 for detectingany signal from the illuminated data element 7, and thereby provide forreading from any of the data elements 7 defined by the information block5.

The illumination unit 33 comprises a light source 37 for providing acollimated light beam 39, and a lens 41 for focussing the collimatedlight beam 39 to provide a converging reading beam 43 which can befocussed at any location within the information block 5 of the mail item1, and thereby enable reading from the data element 7 at that location.In this embodiment the energy density of the reading beam 43 at thelocation of the focal point of the reading beam 43 is such as to providefor one-photon absorption. Thus, any of the data elements 7 can beindividually addressed for reading without the possibility of cross-talkwith adjacent data elements 7.

FIG. 5 illustrates a mail handling system 45 in accordance with apreferred embodiment of the present invention.

The mail handling system 45 comprises an information reader 31 as abovedescribed for reading information from the information block 5 of a mailitem 1, with the three-dimensional array of the information block 5defining a plurality of layers to which information can be written, andidentifying the last written layer of the information block 5 in whichinformation is stored, and an information writer 11, 21 as abovedescribed for writing new information in a subsequent layer of thethree-dimensional array of the information block 5 as required. In oneembodiment the information writer 11, 21 is configured such as toover-write the last written layer of the three-dimensional array of theinformation block 5 and thereby zeroise that layer.

With this configuration, the mail handling system 45 provides for therepeated use of mail items 1; the mail items 1 thereby being re-usable.In not requiring the marking of the mail items 1, such as by printing,to apply, for example, postage indicia, the mail items 1 convenientlyprovide for re-use.

Finally, it will be understood that the present invention has beendescribed in its preferred embodiments and can be modified in manydifferent ways without departing from the scope of the invention asdefined by the appended claims.

1. A mail item incorporating an information block which provides athree-dimensional array of addressable data elements for storinginformation, wherein the three-dimensional array defines a plurality oflayers to which information can be written.
 2. The mail item of claim 1,wherein the information block comprises a carrier including aphotochromic storage material having first and second states, and areadout material for providing an indication of the state of the storagematerial at its location.
 3. The mail item of claim 1, wherein thestored information includes encoded information.
 4. The mail item ofclaim 3, wherein the encoded information is encrypted information. 5.The mail item of claim 3, wherein the encoded information iscryptographically-signed information.
 6. The mail item of claim 1,wherein the information block comprises an applied coating.
 7. The mailitem of claim 1, wherein the information block defines at least part ofa body of the mail item.
 8. The mail item of claim 1, wherein the mailitem comprises a container.
 9. The mail item of claim 1, wherein themail item comprises an envelope.
 10. The mail item of claim 1, whereinthe mail item is re-usable, such that, on each use, information iswritten to a different layer of the information block.
 11. Use, as are-usable item, of a mail item incorporating an information block whichprovides a three-dimensional array of addressable data elements forstoring information, with the three-dimensional array defining aplurality of layers to which information can be written.
 12. A mailhandling system, comprising: an information reader for readinginformation from an information block, as a three-dimensional array ofaddressable data elements, incorporated in a mail item, with thethree-dimensional array defining a plurality of layers to whichinformation can be written, and identifying the last written layer inwhich information is stored; and an information writer for writing newinformation in a subsequent layer of the three-dimensional array of theinformation block.
 13. The mail handling system of claim 12, wherein theinformation writer is configured such as to over-write the last writtenlayer of the three-dimensional array of the information block andthereby zeroise that layer.